1. Field of the Invention
The present invention relates generally to an engine control system for an automotive power train and more specifically to an control system for an automotive power train which includes a torque converter.
2. Description of the Prior Art
JP-A-1-313636 discloses an engine control system to overcome the difficulty in controlling the amount of fuel supplied to the engine during transient modes of operation, the basic engine output shaft torque control utilizes the fuel injection amount and the amount of air being inducted. However, this technique sets a target engine torque output based on the amount of accelerator pedal movement.
In the event that a torque converter is used to provide a drive connection between the engine and a transmission associated with the engine, the amount of torque which is supplied to the vehicle drive shaft or shafts, is not commensurate with the amount of accelerator pedal movement.
By way of example, when a vehicle is moving off from standstill, the accelerator pedal may be deeply depressed and induce a marked increase in engine rotational speed and torque generation. However, under these conditions vehicle acceleration does not increase proportionally. The reason for this is that, by the very nature of the torque converter, the ratio of the torque converter input and output shafts does not assume a 1:1 relationship.
Further, as the characteristic relationship between accelerator pedal movement and drive shaft torque varies with the type of engine, torque converter construction and mode of driving, it is not possible to develop an optimal control relationship.
For example, during cornering, sudden increases in torque is apt to induce vehicle spin, while in the case the vehicle is running in a straight line, such an increase is apt not to produce any problems. Thus, it is left to the driver's discretion to determine the instant driving conditions and to determined when and how much the accelerator pedal movement should be induced.